1. Field of the Invention
The present invention relates to a tactile display device for displaying tactile information and further relates to a touch panel apparatus with such a tactile display device.
2. Description of the Related Art
As such a tactile display method, there is presented a method of controlling an appearance of a convex key by means of an electrorheological fluid (ER fluid), for example (Japanese Patent Application Laid-Open No. Hei 11-273501).
In this method, the electrorheological fluid is sealed within a plate-like receptacle or box disposed above a display device. Then, an electrical power distribution over this fluid is controlled in such a manner that a part or area of the electrorheological fluid (i.e. the fluid which viscosity is changed by electricity) corresponding to the convex key is relieved or embossed by means of a pump as a pressure device. As a result, an embossed key can be appeared.
Furthermore, there is also presented a technology for applying a counterforce to a display element in response to a deformation, by means of an electrorheological fluid (Japanese Patent Application Laid-Open No. 2000-89895 and so on).
However, the aforementioned related arts have a problem as described below.
In order to change the viscosity of the electrorheological fluid, it is necessary to control voltage which is applied to the electrorheological fluid, in accordance with “a pattern to be displayed” (hereinafter referred to as a “display pattern” as appropriate) and the like. Therefore, a special device for performing such a control is required, which increases a size of the apparatus and/or causes heavy-duty operation. That is, from a technical viewpoint, it is difficult to display the tactile information efficiently.